Before she had the chance to don her teenie weenie bikini at Coachella this weekend, Tallulah Willis was seen smoking a suspicious looking cigarette in a random alley in Venice Beach.

According to the photographer who took the photos, the 19-year-old "grabbed a medical vial out of her little backpack and pulled out what appeared to be a joint with a plastic filter on it – just like the ones you buy at the medical marijuana places in Venice — and she started to smoke."

The photographer says that the two did some shopping and grabbed some grub before hopping into their chauffeured SUV to head to the event.

He went on to tell us, "She was worried and trying not to be seen, hiding behind a dumpster."

Tallulah's mom Demi Moore checked into rehab last July after an apparent overdose in January. Demi's split from Ashton Kutcher sent her into an intense party phase and one night, as she smoked spice with friends, she suffered what seemed like seizures and was rushed to the hospital.